Yeah, definitely focus on the fact that this attack is to kill the emperor. The death star in ANH was an immediate threat and the attack on it was to defend the yavin base. This attack is entirely different - it is an attempt to make a decisive strike at the heart of the Empire and win the war. I also like the idea of altering the death star to look even less finished than it does in ROTJ.

EDIT: Over in the General Star Wars section there's an interesting debate happening about the actual timeframe of the movies, i.e over what length of time do they each take place? The most problematic film is ESB - how long is Luke training for? How long does it take Han and Leia to get to Bespin? Irvin Kershner says it takes place over a period of a few months, yet the characters don't even change their clothes. Are there any plans to address this issue in the Starkiller edit? (not the lack of a change of clothing, but just the ambiguity of the passing of time). Apart from a caption reading '2 months later' I can't think of any ideas, but maybe you guys can.